Numerous machines have been developed specifically for comminuting empty glass containers. By breaking containers into fragments, the recycling or disposal of glass material is facilitated. Machines developed for this purpose typically include an inlet opening through which the glass containers are inserted and an outlet opening through which the broken glass fragments and glass dust are ejected. To accomplish the breaking of the glass, these machines usually employ either a crushing apparatus or a hammermill form of breaker apparatus.
A significant problem with prior art machines that employ a crusher-type apparatus is a susceptibility of the machine to jamming when metal or plastic is inadvertently dropped into the machine's inlet. To overcome this difficulty, the machine will either have the ability to crush the metal, or it will include an automatic dump apparatus that allows the machine to purge its contents when the anvil of the crushing mechanism meets an unusual resistance. Both of these solutions add an undesirable measure of complexity and expense to the device.
In machines that employ a hammermill type of breaking apparatus, frequent and expensive maintenance is often required. The hammermill is usually comprised of a number of rigid metal "hammers" that are mounted on the exterior surface of a central rotatable shaft. Each hammer must be sharp and straight for the machine to operate efficiently. However, during use the individual hammers rapidly become dulled. In addition, metal objects inadvertently fed into the device can bend or break the hammers, necessitating repair or replacement of the damaged hammers.
One modification that has been used somewhat successfully in overcoming the failings of the prior art hammermills is the use of flexible hammers or "flails" in lieu of rigid hammers. The flexible flails are typically in the form of sections of conventional multi-link chain attached to the machine's central shaft in a spaced-apart configuration. The chains break the glass and allow any metal fragments or metal containers to rapidly pass through the device without causing any damage.
The flexible chain type of hammers, while providing a number of advantages over the prior art rigid hammers for hammermills, still suffer a number of failings. Firstly, the degree of comminution is uncontrolled, and as a result relatively large diameter fragments of glass are often ejected from the device outlet. Since the outputted material includes these large glass shards or fragments mixed with the smaller glass particles, the material cannot be easily recycled and is difficult to handle. For example, a major use of pulverized glass is in road construction where the pulverized glass is mixed with asphalt or similar materials. The large glass fragments would make the mixture unsuitable for this application.
A second problem with prior art chain-type hammermills is that the layout of the device normally requires either a gravity or blower induced flow of material through the device in order to prevent the material from clogging the unit. As a result, the machine requires a large foundation. In addition, use of a blower to enhance flow through the device entails a significant increase in operating and maintenance costs.
A third problem with prior art devices is that the flowpath of the material within the machine is inefficient and uncontrolled. This results in the high speed ejection of minimally broken material from the device's outlet. This high speed material can cause damage to whatever container or surface is being used to receive the broken glass.
Furthermore, present methods of fastening chain-type flexible flail hammers to the rotatable shaft can cause premature wear in both the attachment end of each flail and in the shaft itself. This can necessitate early replacement of the flails and/or replacement or machining of the shaft.
Finally, the conventional chain from which multilink chain flails are fabricated is not normally manufactured of hardened steel; chain flails used in the harsh glass comminution service typically require replacement at inconveniently short intervals.